Ultrasound has revolutionized pregnancy monitoring. Its routine use has in other prenatal diagnosis of fetal pathologies, it is the other reference screening tool of the most common obstetric pathology, preterm labor. Its use became widespread in the delivery room, the presence of an ultrasound machine is recommended by the decrees of perinatal care in maternity hospitals performing more than 1,500 deliveries per year. It is natural for conducting ultrasound during labor has emerged, first to help identify the variety of the presentation of the fetal head and then more recently in aid to instrumental delivery. Several studies have shown that ultrasound had a sensitivity of commitment over 90% for predicting the success of instrumental extraction and a vaginal delivery.